Acquired immune deficiency syndrome (AIDS) is caused by a group of retroviruses known as HIV (Barre-Sinoussi et al., Science 220:868-871, 1983; Gallo et al., Science 224:500-503, 1984; Coffin et al., Science 232:697, 1986). The first member of the group has been designated HIV-1 and is responsible for a majority of cases of AIDS worldwide. It is distinguished from HIV-2, an isolate discovered from WAf (Clavel et al., Science 233:343-346, 1986). Although HIV-2, like HIV-1, produces symptoms of immune deficiency in man, it is also genetically distinct from HIV (Guyader et al., Nature 326:662-669, 1987).
The genomes of the HIV isolates, like those of other retroviruses, include three basic genes: gag, pol and env (Weiss et al., Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y., 1985). In addition, the genomes contain several other genes whose products play important roles in the regulation of viral gene expression (Dayton et al., Cell 44:941.947, 1986; Fisher et al., Nature 320:367-371, 1986; Sodroski et al., Nature 321:412-417, 1986).
HIV-1 is typically transmitted by sexual contact, by exposure to blood or certain blood products, or by an infected mother to her fetus or child (Piot et al., Science 239:573-579, 1988). The first examples of transfusion-associated HIV-2 infection have been disclosed (Courouce et al., AIDS 2:261-265, 1988). Therefore, the demand for sensitive and specific methods for detecting HIV in contaminated blood or blood products is significant.
EIAs, based on whole virus or viral lysate, have been developed for the detection of HIV. However, it has been found that the EIAs have unacceptable, non-specific reaction with specimens from individuals with non-HIV conditions such as autoimmune diseases, a history of multiple pregnancies, anti-BLA, EBV infections or hypergammaglobulinemia.
In order to avoid such non-specific reactions and in an attempt to detect anti-HIV-1 and/or anti-HIV-2 in samples, an ELISA has been developed and commercialized by Abbott Laboratories for serological diagnosis of HIV infection using the HIV-I core and HIV-1 envelope and HIV-2 envelope proteins. However, this ELISA has not provided the highly specific, highly sensitive detection needed for superior protection of the blood supply, or for early diagnosis of HIV in a patient.
Thus, in order to provide superior protection of the blood supply, and in order to provide superior diagnosis of HIV in a patient, there has gone unmet a need for products and methods capable of highly specific, highly sensitive detection of HIV. There has also gone unmet a need for products and methods capable of eliciting an immune response to HIV, especially an immunoprotective immune response to HIV. The present invention provides these and other related advantages.
In addition to the problems associated with HIV, other positive-stranded RNA viruses also pose significant health risks throughout the world. One example of such a positive-stranded RNA virus is the Hepatitis C virus (HCV). HCV is distinguishable from other forms of viral-associated liver diseases caused by known hepatitis viruses such as hepatitis A virus (HAV) and hepatitis B virus (HBV). Like HIV, HCV is often transferred via blood transfusion; post-transfusion hepatitis (PTH) occurs in approximately 10% of transfusion patients, and HCV (i.e., Non-A, Non-B hepatitis (NANBH)) accounts for up to 90% of these cases. A major problem arising from this disease is the frequent progression to chronic liver damage (25-55%). Therefore, the demand for sensitive, specific methods for detecting HCV in contaminated blood or blood products is significant.
The hepatitis C virus (HCV) was first identified by molecular cloning and characterization of its RNA genome by Choo et al. (Science 244:359-362, 1989). A specific assay using an HCV antigen designated C100-3 was then created, using recombinant DNA methods in yeast. The assay detects an antibody against HCV (Science 244:362-364). A detailed disclosure of the genome of HCV, and some cDNA sequences and polypeptides derived therefrom, as well as methodologies relating to such subject matter, is provided in EP 0 318 216 A1 in the name of Chiron Corporation. In particular, this disclosure provides a synthesized polypeptide, C100-3, containing 363 virally-encoded amino acids that can be used for the detection of one type of HCV antibody. Presently, kits for detecting HCV antibodies on the basis of the C100-3 antigen have been commercialized by Abbott Laboratories.
As suggested in EP 0 318 216 A1, HCV may be a flavivirus or flavi-like virus. With respect to general morphology, a flavivirus contains a central nucleocapsid surrounded by a lipid bilayer. It is believed that hepatitis C virus protein is composed of structural proteins including a nucleocapsid (core) protein (C), two glycosylated envelope proteins (E1, E2) and several nonstructural proteins (NS-5). It has been confirmed that C100-3 disclosed by Choo et al. is a protein encoded by part of nonstructural regions 3-4 of the HCV genome. It has been found that anti-C100-3 antibody is not detected in all post-transfision NANBH cases. The failure to detect the anti-C100-3 antibody is possibly due to hypermutation of the nucleotide sequence in C100-3 region.
In addition to the work with the nonstructural C100-3 antigen, an enzyme-linked immunosorbent assay (ELISA) has been developed for serological diagnosis of hepatitis C virus (HCV) infection using the HCV core protein (p22). The core protein was synthesized by a recombinant baculovirus, as reported in Chiba et al. (Proc. Natl. Acad. Sci. USA 88:4641-4645, 1991). Thus, the assay of Chiba, et al. used a nonglycosylated 22-kDa nucleocapsid (core) protein, in an effort to establish an antibody-based, specific, sensitive method for diagnosing HCV infection. However, this core protein-based assay failed to detect a significant number of cases of HCV infection, even when relatively large sample volumes were available.
Thus, as with other positive-stranded RNA viruses, there has gone unmet a need for products and methods capable of highly specific, highly sensitive detection of HCV. There has also gone unmet, as with other positive-stranded RNA viruses, a need for products and methods capable of eliciting an immune response to HCV, especially an immunoprotective immune response to HCV. The present invention provides these and other related advantages.